Simulation Model Evaluation of Some Fisheries Balance Indicators

Chronic overcapacity has been identified as a major cause of the overfishing of Europe¿s fish stocks and the poor economic performance of the European fishing fleets. Mechanisms are needed to ensure that the capacity of European fishing fleets remain proportionate to available fish stocks. To that end, the European Commission developed ¿Guidelines for an improved analysis of the balance between fishing capacity and fishing opportunities¿, which specify a minimum set of fleet-based technical, biological, economic, and social indicators that purportedly measure the balance between fishing fleets and fish resources. A bioeconomic simulation model was developed to assist in the evaluation of some of these balance indicators. The model is age-structured, like standard single-species stock assessment models, but accommodates multiple independent fish stocks that are harvested by multiple independent fishing fleets. The fish stocks occupy multiple spatial regions with diffusion of fish between regions. The fishing fleets choose where and how to fish based on anticipated profits. Randomness is included in the simulated system in the annual fish recruitments and their spatial distribution. The model was used to generate a series of balance indicators that were then compared against the true conditions in the simulated fisheries to evaluate whether the indicators provide accurate signals of system status. The simulations showed that randomness in recruitment propagates directly into randomness in the balance indicators implying that it will be difficult to detect meaningful signals from any short time series of balance indicator values.JRC.DG.G.4-Maritime affair